Aggregatibacter actinomycetemcomitans (Aa) is intimately associated with Localized Aggressive Periodontitis (LAP) in young adults. Further, Aa possesses a variety of virulence traits that are consistent with pathogenic events that occur in LAP. Our group has been studying genes that are related to Aa-induced disease initiation and as such encode virulence traits responsible for Aa attachment, colonization, persistence, and subgingival survival. Thus far we have ascribed functions for two Aa autotransporter adhesin genes (aae and apiA) that are related to the specificity of Aa attachment to epithelium and have shown that these adhesins (as well as Leukotoxin) show species specificity for Old World (OW) primates and humans. This specificity makes the OW primate an ideal model for studying early events related to Aa infection with an eye toward development of preventive strategies. This R21 application consists of two Aims and is designed to compare oral colonization and persistence of two Aa strains (one from humans and one from Rhesus [Rh] monkeys) that are introduced into the oral cavity of OW primates. Each strain will be examined for its pattern, level of attachment, and colonization at different times over a 28-day period following introduction into the mouth of the monkey.
Aim 1 will describe the topographical and quantitative level of Aa found in the mouths of Rh monkeys initially and then compare colonization and persistence of the two strains of Aa (one human and one monkey). Before placement, monkeys will receive scaling and prophylaxis plus chlorhexidine treatment. Animals will be fed Aa in a pancake and colonization and persistence will be analyzed 28 days after feeding. The Aa that colonizes and persists on teeth at a level equal to or greater than 1 x 102 /mL colonies of Aa will be selected for use in Aim 2.
Aim 2 will assess the location, level and timing of Aa found on BECs, tongue and teeth comparing un-inoculated and wild type inoculated Aa to Aa with mutations in aae and apiA, a double knockout of aae/apiA, flp (the fibrillar outer protein) and ltx over a 28-day period. These experiments should reveal the importance of these genes in relation to Aa attachment to BECs (aae and apiA), to tooth colonization (flp) and to subgingival survival (ltx) in the oral cavity of OW primates. Establishing the utility of this model should allow us not only to dissect out attachment factors but also to unravel immune modulation factors from other Aa genes as they affect Aa pathogenesis in the future with an eye toward preventive strategies.
Aggregatibacter actinomycetemcomitans is intimately associated with Localized Aggressive Periodontitis in young children, which can result in premature loss of teeth. Coincidentally, A. actinomycetemcomitans is also found in the mouths of Old World primates such as Rhesus (Rh) monkeys. It has been shown that A. actinomycetemcomitans attaches to tissues and kills defense cells in humans and Rh monkeys in a very similar manner. Therefore the Rh monkey provides us with an ideal model in our efforts to unravel some of the mysteries related to the earliest stages of A. actinomycetemcomitans-induced disease. It is also known that A. actinomycetemcomitans produces several factors that are similar to many other bacteria that cause severe infections in man. Therefore, studying A. actinomycetemcomitans in the mouth of Rh monkeys can provide a model that can help us understand how A. actinomycetemcomitans-induced infections develop in a real world environment. This understanding may also have application for other mucosal diseases. We have developed a relationship with the Northeast Primate Research Center and have designed a study that will enable us to place this bacterium in the mouths of Rh monkeys. This study design will allow us to examine how genes direct the way in which A. actinomycetemcomitans attaches to tissues and initiates disease. While attachment is recognized as the first step in infection of skin surfaces that include surfaces like the gums, survival depends on the ability of the bacteria to defend itself against host defense cells. This proposal is designed to examine how certain A. actinomycetemcomitans genes influence early events such as attachment and survival below the gum line. Use of this primate model will allow us to develop ways to interfere with attachment and survival in the hope that we can devise strategies to prevent infections without the need to resort to the use of antibiotics. )
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